Totally agree that the sensors are notoriously inaccurate, and 70% accuracy may be too optimistic. When we picked up our brand new TT last year, before any use at all, our tank showed FULL. Not likely. Probably a small piece of debris in the installation process. When we had our HTT prior to the TT, at first we fretted over what the sensors showed, then found that our own experience was much more accurate.
Lots of methods of breaking down the waste and eliminating odors. The Geo Method is popular, and while we haven't tried it, believe we'll give it a shot next spring. We've used Odorlos for several years and had no problems and no odors.
Skimping on the water is one of the main causes of problems with the black tank. Suggest you use water going into the grey tank like you're paying for it by the gallon....be very thrifty. Be very generous on the black tank. Contrary to what many suggest, we dump after every weekend BUT...at that time we put in the required amount of Odorlos and about 5 gallons of fresh water. Never, never let the black tank sit totally empty. Any remaining waste will be like concrete.
You'll learn in short time about how long you can leave your black tank before you need to dump. In both the HTT and TT, even on longer trips, we've gone several days without dumping and no problems.
Agree on the clear fitting for the stinky slinky. You can actually see what's going on and if you have any clogs. BTW, do not leave the valve open on the black tank when you have full hookups. You need to build up an adequate amount of liquids to work with the solids so wait until last thing before you leave to dump. Your camping neighbors likely won't even notice that you have a clear fitting since nothing is coming out until you actually dump. You can dump the grey tank as often as you need to and then close the valve. The warning sign that the grey tank needs to be dumped NOW is when it starts to back up into the shower. The only time we had this happen, I thought there might be a clog in the plumbing from the kitchen sink as it drained very slowly. Went in to check the bathroom sink and the shower was about 1" from overflowing. Note to self! If you find that your trips are more than 2 - 3 days and you have very full grey tank, suggest you look into a blue tote.